Sound-responsive light

ABSTRACT

A sound-responsive light illuminated by an audio-actuated serially connected switch. The audio-actuated switch includes a thyristor, preferably an SCR, the gate of which is triggered by an audio frequency signal from a microphone and audio amplifier. The amplifier is a class A audio amplifier with biasing and loading provided so that the light will be illuminated by sound above a selected level. A nonlinear potentiometer is used for the load impedance of one of the amplifier stages to permit selection of the desired audio level which triggers the thyristor. The input terminals of a rectified power supply are connected across the principal terminals of the SCR so that the parallel combination may be connected in series with the electric light and an alternating current power source. Coupling is provided from the output of the audio amplifier to the gate of the thyristor by means of a series capacitor and a shunt gate resistor of approximately 1000 ohms.

[72] Inventor James H. Ott

Columbus, Ohio [21] Appl. No. 839,524 [22] Filed July 7,1969 [45]Patented June 1, 1971 [73] Assignee Novar Electronics CorporationBarberton, Ohio [54] SOUND-RESPONSIVE LIGHT 10 Claims, 4 Drawing Figs.

[52} U.S.Cl 307/117, 340/148, 307/252 [51] Int.Cl ..H01h 37/00 [50]Field of Search 307/117,

ll6,112,l32,252,2l;340/258,259,148,171

[56] References Cited UNITED STATES PATENTS 2,954,489 9/1960 Brueggeman307/1 l7 3,270,216 8/1966 Dersch 307/117 3,440,347 4/1969 Spencer et al.307/l 17X 3,475,092 10/1969 Harvey 307/1 17X Primary ExaminerRobert K.Schaefer Assistant Examiner-HJ. Hohauser Attorneys-Frank H. Foster andJerome R. Cox

ABSTRACT: A sound-responsive light illuminated by an audio-actuatedserially connected switch. The audio-actuated switch includes athyristor, preferably an SCR, the gate of which is triggered by an audiofrequency signal from a microphone and audio amplifier. The amplifier isa class A audio amplifier with biasing and loading provided so that thelight will be illuminated by sound above a selected level. A nonlinearpotentiometer is used for the load impedance of one of the amplifierstages to permit selection of the desired audio level which triggers thethyristor. The input terminals of a rectified power supply are connectedacross the principal terminals of the SCR so that the parallelcombination may be connected in series with the electric light and analternating current power source. Coupling is provided from the outputof the audio amplifier to the gate of the thyristor by means of a seriescapacitor and a shunt gate resistor of approximately 1000 ohms.

I THYRISTOR Q SWITCH PATENTEUJUN IIBYI 3582.871

sum 1 [IF 2 FIG IS INVENTOR. JAM ES H. OT T W mwffimbb ATTORNEY PATENTEDJUN llQYl 3,582,671

SHEET 2 BF 2 F I G 4 I NVENTOR.

JAMES H OTT ATTORNEY BACKGROUND OF THE INVENTION This invention relatesto an audio-actuated electrical device, and more particularly relates toan electric light which is illuminated in response to the presence ofsound above a selected level.

Electric lights have traditionally been used for a variety of purposesincluding illumination and signalling. I have found that there is a needfor a device which can provide an instantaneous, active, visualrepresentation of an immediate sound environment.

As an example, many persons have found it pleasurable to listen tostereo music with the aid of stereo earphones. However, with suchearphones positioned over the listeners ears, and with music beingreproduced by the earphones, a listener, relaxing in a chair, would beunable to hear a ringing telephone or a statement made to him by anotherperson standing in the room. However, with the aid of my audio-actuatedlight, such sounds would be immediately indicated to the listener.

The audio-actuated light also can find use with children born withouthearing, or other persons hard of hearing or deaf. My light is useful inteaching such persons to speak because it gives an immediate indicationof the effect of their voices, especially the magnitude of the voices.Furthermore, the characteristics of the light flicker vary somewhataccording to the type of sound reaching the light. Therefore, myaudio-actuated light can be used to indicate the nature of a sound.

My light can also be used in places such as libraries, hospitals, orstudy rooms where a low level of noise is desired. Such a light wouldflicker when the sound level rises above an acceptable level and shouldserve as an alarm to discourage the making of such noise. Thesound-responsive light is also an effective tool for deterring burglarsand thieves. For example, the noise created by the opening of a window,walking, or the removal of loot, would create a flash or flashes oflight which should alert neighbors and possibly scare a thief or causehim to flee.

The audio-actuated light can also have an interesting effect onconversation between two or more persons. The illumination of the light,modulated by the speaker's voice, seems to make a person more consciousof his manner of speaking. Finally, a light which is audio responsivewill provide a stimulus for teaching a songbird to sing by reinforcinghim for his sounds. A captive bird, such as a canary, may be rewardedfor its singing by the pleasing light variations created by my light inresponse to his sounds. In effect, this would be a teaching machine forthe canary which would not require the attention of the owner.

It is therefore an object of my invention to provide an improvedaudio-actuated switch.

Another object of my invention is to provide an improved audio-actuatedillumination means.

Another object of my invention is to provide an audio-actuatedillumination means which is instantaneous in that there is noperceptible time delay between the beginiiing or the cessation of audiostimulus and the beginning or cessation of the illumination.

It is a further object of my invention to provide a light which isilluminated in a manner characteristic of its audio stimulation. BRIEFDESCRIPTION OF THE DRAWINGS FIG. I is a block diagram of the invention.

FIG. 2 is a schematic diagram of the preferred embodiment of theinvention.

FIG. 3 is a mixed schematic and block diagram illustrating analternative embodiment of the invention.

FIG. 4 is a schematic view illustrating another alternative embodimentof my invention.

In describing the preferred embodiment of the inventionillustrated inthe drawings, specific terminology will be resorted to for the sake ofclarity. However, it is not intended to be limited to the specific termsso selected, and it is to be understood that each specific term includesall technical equivalents which operate in a similar manner toaccomplish a similar purpose.

SUMMARY OF THE INVENTION FIG. I illustrates the general principals ofthe invention. The invention comprises a transducer, such as amicrophone l, for converting an input mechanical audio signal, such assound waves in air, to an electrical audio signal output. A thyristorhaving a control gate 2 is provided with suitable circuitry to operateas a switch 3. Means, such as an audio amplitier 4, is connected betweenthe output of the transducer I and the gate 2 of the thyristor switch 3for impressing an audio frequency trigger signal derived from thetransducer on the gatev 2. The principal terminals 5 and 6 of thethyristor are connected to an electrical device 7, such as an electriclight, which is series connected to a source of electrical energy 8 inorder to control the electrical current flow through the electricaldevice 7.

The word thyristor is used to include not only the more commonly knowndevices such as the triac and silicon-controlled rectifier which Iprefer to use, but also other types of controlled rectifiers such asthyratrons, devices not yet so popularly known, and devices yet to beinvented which exhibit the characteristics necessary for switching inthe manner of my invention.

Furthermore, I have chosen the word signal and intend it to include notonly ordinary sinusoidal waveforms but also pulses of various shapes.Thus when I refer as in the above summary, to an audio frequency triggersignal on the gate of the thyristor, I mean a signal which exhibitssubstantial magnitude variations at an audio rate. I do not include inthe term audio frequency signal, a voltage or current which, although itmay have some audio or ripple noise present, is used for its averagevalue averaged over several audio or ripple cycles.

DETAILED DESCRIPTION Briefly described, the preferred embodiment of myinvention, as illustrated in FIG. 2, has a source of electrical energywhich is a 117 volt outlet at terminals 9 and 10 of the type commonlyavailable in a home, in series connection with a mechanical on-offswitch II, an electrical device such as light 12, and a thyristor suchas the SCR 13, which has a control gate 14. The principal terminals 15and 16 of the SCR 13 are connected in series with the light 12 and thesource of electrical energy at terminals 9 and It). The SCR I3 operatesas a switch which will permit or prevent current flow through the light12. A microphone l7 converts an input mechanical audio signal, such assound waves, to an electrical audio signal output. The electrical audiosignal output from the microphone 17 is amplified by the class A audioamplifier I8 and then impressed on the gate 14 of the SCR I3.

In more detail, the preferred embodiment has a microphone 17 which isconnected to the input of a first audio amplifier stage having atransistor 19 with a load resistor 20. For a ceramic microphone I use aDarlington pair. The amplified output from the transistor I9 is directlycoupled to the next audio amplifier stage having a transistor 22 andbiasing and load resistors 24 and 26 respectively. An emitter capacitor28 is provided to perform its conventional function of bypassing thesignal around the resistor 24. The load resistor 26, which I prefer, isthe stator of a nonlinearly varying potentiometer. The adjustable wiper30 of the potentiometer provides a variable audio sensitivity controland is connected by a coupling capacitor 32 to the input of a thirdaudio amplifier stage having a transistor 34. A feedback resistor 44 isprovided for temperature stability and biasing. The third stage has aload resistor 42 and a feedback resistor 43 for providing operating biasand stability. The output from the third transistor 34 is coupled to thegate 14 of the SCR 13 by a capacitance 48. A gate resistor 50 isprovided for biasing and current overload protection and to preventfloating of the gate.

A rectified power supply 51 for biasing and supply power to the audioamplifier 18 is connected across the principal terminals 15 and 16 ofthe SCR 13. This is preferred so that all of the electrical circuitrywhich makes up the audio-actuated switch can be connected in series withthe light 8 and the source of power at terminals 9 and 10. With such aconnection, removal or burning out of the light 8 completely deenergizesthe audio-actuated switch circuitry. Furthermore, the light 8 serves asan impedance which limits the current through the audio-actuated switch.The half-wave power supply 15 illustrated comprises an input resistor52, a diode 54, a filter resistor 56, and a pair of filter capacitors 58and 60.

Although the power supply can be connected across an SCR it ordinarilycan not be connected across a triac. With an SCR, the on time neverexceeds one-half cycle so that the other half-cycle is available for therectified power supply 51. A triac may be on for a full 360 thus ineffect shorting any power supply connected across its principalterminals. However, an alternative arrangement using a triac isillustrated in FIG. 3 and described below.

In the preferred embodiment of FIG. 2, the series-connected light 12,SCR 13 and power source at terminals 9 and 10 are arranged so that theamplifier and the bulb socket are both at signal ground. This is done toreduce the coupling of any spurious noise from the power lines to theamplifier which might cause firing of the SCR. Several noise sourcesexist in a home and examples include light dimmers and electric motors.

The operation of the preferred embodiment begins with the closing of themechanical switch 11. With the switch 11 closed, the light 12 is readyto be illuminated. In the absence of sound in the environment of themicrophone 17, no trigger signal will be present at the gate 14 and thelight 12 will not be illuminated. If sound is incident on the microphone17, the sound will be converted to an electrical audio signal andamplified by the stages of the audio amplifier 18. An audio signal willbe present at the gate 14. If the peaks of the audio signal at the gate14 are below the gate-firing voltage, the lamp will still not beilluminated; if, however, the peaks of the audio signal at the gate 14are greater than the gate-firing voltage, the lamp 12 will be energizedduring part of each half-cycle that the principal terminals 15 and 16 ofthe SCR 13 are forward biased.

The magnitude of the audio signal of the gate 14 is dependent not onlyon the level of sound input to the microphone 17 but also on theposition of the wiper along the resistance 26. Thus, the wiper 30 is asensitivity control which can be adjusted so that a desired sound inputlevel fires the SCR 13. Preferably, the resistance 26 varieslogarithmically in order to give good control at low levels of audioinput to the microphone 17 as well as at higher levels.

In the preferred circuit, then, the voltage at the gate 14 is an audiosignal resulting from the sound input to the microphone 17. Within anamplitude range for each setting of the wiper 30 the amplitude of thegate signal controls the apparent brightness of the lamp 8. The SCR willalmost always be fired at or near the beginning of its conductinghalf-cycle if the magnitude of the gate signal is sufficient because theaudio signal frequency is ordinarily at least ten times larger than thefrequency of its source of electrical energy at terminals 9 and 10(which is applied to the principal terminals of the SCR).

Most sounds, such as that of a human voice, are continuous streams ofvarying magnitude. If the wiper is positioned to make the circuit verysensitive, almost all spoken sound will illuminate the lamp.

If a low sensitivity is used only the occasional higher magnitude soundwill cause the light to be energized. The lamp will be energized foronly a few half-cycles. At an intermediate sensitivity, the apparentbrightness of the light will seem to flicker during a series ofutterances depending upon the relative number of half-cycles the lamp isnot energized.

One important feature of the preferred embodiment is that, because thetrigger pulses at the gate 14 are at the same frequency as the input atthe microphone 17, there is substantially no visible time delay from thetime the sound ceases at the microphone 17 until the time that the light12 is no longer illuminated. This enables the light 12 to flicker morenearly and closely in response to the words and syllables of a speakertalking into the microphone 17. At the beginning of a sufficiently loudword or syllable the light will be immediately illuminated; and when theword is ended or a sentence is ended, it will immediately shut off. Thisgives the speaker a great awareness that the light is indeed directlyreacting to his voice. Conventional audioactuated switches providerectifier and filter capacitors which rectify and filter the audiosignal. This results in a light which will be turned on in aconventional system in response to the sound but which when the soundstops, especially for a small instant of time, maintains the light onuntil the capacitor can decay. Such a system is not intended to give anddoes not give a close correspondence between the light illumination andthe sounds of a speaker.

The coupling of the output of an audio amplifier by a capacitor to thegate of a thyristor is believed to be new. To accomplish this, I haveused a capacitor which provides an impedance 18, small enough so thatthe input impedance to the gate circuit as the terminal 62 and ground ismatched with the output impedance of the third transistor 34 amplifierstage.

It is the intention of my invention that any suitable means could beused to connect the output of the transducer 17 to the gate 14 of thethyristor 13 for impressing an audio frequency trigger signal on thegate. Some clipping of the signal is permissible so that one or more ofthe transistors 16, 22 and 34 could be biased to operate class AB, classB or class C. These would in effect clip offa portion of the audiosignal. Also substantial nonlinear distortion of the audio signal ispermissible and therefore the amplifier stage can be operated in thenonlinear range of their characteristics. It is only necessary that theaudio rate of substantial magnitude variation be preserved. Therefore,even with clipping or distortion and provided there is no smoothingcapacitor used anywhere, an audio frequency trigger signal will beimpressed upon the gate 14. Such a signal will provide operation verysimilar to that provided by the preferred embodiment illustrated inFIG. 1. Such operation would, unlike previously known circuits, providea light flicker which appears to be an instantaneous representation ofthe audio input to the transducer 17.

In FIG. 3, I illustrate an alternative embodiment of my invention. Itillustrates two alternatives. First it illustrates the use ofa triac 113rather than an SCR and second it illustrates a rectified power supply151 which is not connected parallel to the thyristor switch.

The circuit of FIG. 3 has a microphone 117 which provides an electricalaudio signal input to the audio amplifier 118. The output of theamplifier 118 is coupled by a capacitor 148 onto the gate 114 of thetriac 113. A standard l 17 volt house voltage may be connected at theterminal 109 and so that when the triac 113 is conducting, the light 112will be illu minated.

In FIG. 4 I illustrate yet another embodiment of my inven tion. Thiscircuit has a full-wave rectifier (but no filtering) connected to analternating source of electrical energy at ter minals 202 and 203 sothat the source of electrical energy at terminals 209 and 210 isfull-wave rectified sinusoid. This rectification provides solelypositive half-cycles on the SCR 213 so that its principal terminals areessentially always biased for conduction. Conduction can then occur fornearly the full 360 therefore providing the advantage of triac-typeoutput with SCR gate sensitivity.

Since rectification is provided by the full-wave rectifier 201, only afilter 255 need be connected to the rectifier 201 in order to providepower supply to the amplifier 218 having a microphone 217.

It is to be understood that while the detailed drawings and specificexamples given described preferred embodiments of my invention, they arefor the purposes of illustration only, that the apparatus of theinvention is not limited to the precise details and conditions disclosedand that various changes may be made therein without departing from thespirit of the invention which is defined by the following claims.

I claim:

1. An audio-actuated switch for controlling electrical current flowthrough an electrical device which is in series with a source ofelectrical energy, the switch comprising:

a. a transducer for converting an input mechanical audio signal to anelectrical audio signal output;

b. a thyristor having a control gate, the principal terminals of thethyristor being in series with the electrical device; 1

and

c. means connecting the output of the transducer to the gate of thethyristor for impressing on said gate a nonfiltered audio frequencytrigger signal, derived from the transducer, for producing instantaneouson and off operation of the electrical device.

2. A switch according to claim 1, wherein said means comprises an audioamplifier, biasing means,

and coupling means.

3. A switch according to claim 2, wherein the audio amplifier is a classA amplifier and the gate trigger signal is substantially analogous tothe mechanical audio signal.

4. A switch according to claim 2, wherein the thyristor is an SCR,

wherein there is provided a rectified power supply, for biasing andsupplying power to said audio amplifier, the power supply having twoinput terminals connected to the principal terminals of the SCR,

wherein said source of electrical energy, said electrical device, andthe parallel combination of the SCR and the rectified power supply areseries connected so that disconnection of the electrical devicedeenergizes the SCR and the rectified power supply and so that thecurrent through the SCR and the power supply is limited by the impedanceof the electrical device.

5. A switch according to claim 2, wherein the audio amplifier comprisesa plurality of amplifier stages, one of the stages having a loadimpedance comprising the stator of a potentiometer and having the wiperof the potentiometer coupled to the input of the subsequent stage forpermitting variable adjustment and selection of a desired audio signallevel for triggering the thyristor.

6. A switch according to claim 5, wherein the impedance along the statorof the potentiometer is logarithmic.

7. An audio-actuated light for illumination in response to sound,

the light comprising a switch according to claim 1, wherein saidelectrical device is an illumination means.

8. An audio light according to claim 7, wherein said source ofelectrical energy is an alternating current.

9. An audio light according to claim 8, wherein the connecting meanscomprises an audio amplifier and coupling means for impressing an audiosignal on the gate which is derived from said mechanical audio signaland wherein biasing means is provided for triggering the gate inresponse to a selected audio level.

10. An audio-actuated light comprising a switch according to claim 4,wherein a. the electrical device is a light;

b. the amplifier is an audio amplifier for providing a gate triggersignal which is derived from the input mechanical audio signal and theamplifier comprises a plurality of amplifier stages, one of the stageshaving a load impedance comprising the stator of a nonlinearly varyingpotentiometer and having the wiper of the potentiometer coupled to theinput of the subsequent stage for variable adjustment and selection ofan audio signal level which triggers the thyristor.

1. An audio-actuated switch for controlling electrical current flow through an electrical device which is in series with a source of electrical energy, the switch comprising: a. a transducer for converting an input mechanical audio signal to an electrical audio signal output; b. a thyristor having a control gate, the principal terminals of the thyristor being in series with the electrical device; and c. means connecting the output of the transducer to the gate of the thyristor for impressing on said gate a nonfiltered audio frequency trigger signal, derived from the transducer, for producing instantaneous on and off operation of the electrical device.
 2. A switch according to claim 1, wherein said means comprises an audio amplifier, biasing means, and coupling means.
 3. A switch according to claim 2, wherein the audio amplifier is a class A amplifier and the gate trigger signal is substantially analogous to the mechanical audio signal.
 4. A switch according to claim 2, wherein the thyristor is an SCR, wherein there is provided a rectified power supply, for biasing and supplying power to said audio amplifier, the power supply having two input terminals connected to the principal terminals of the SCR, wherein said source of electrical energy, said electrical device, and the parallel combination of the SCR and the rectified power supply are series connected so that disconnection of the electrical device deenergizes the SCR and the rectified power supply and so that the current through the SCR and the power supply is limited by the impedance of the electrical device.
 5. A switch according to claim 2, wherein the audio amplifier comprises a plurality of amplifier stages, one of the stages having a load impedance comprising the stator of a potentiometer and having the wiper of the potentiometer coupled to the input of the subsequent stage for permitting variable adjustment and selection of a desired audio signal level for triggering the thyristor.
 6. A switch according to claim 5, wherein the impedance along the stator of the potentiometer is logarithmic.
 7. An audio-actuated light for illumination in response to sound, the light comprising a switch according to claim 1, wherein said electrical device is an illumination means.
 8. An audio light according to claim 7, wherein said source of electrical energy is an alternating current.
 9. An audio light according to claim 8, wherein the connecting means comprises an audio amplifier and coupling means for impressing an audio signal on the gate which is derived from said mechanical audio signal and wherein biasing means is provided for triggering the gate in response to a selected audio level.
 10. An audio-actuated light comprising a switch according to claim 4, wherein a. the electrical device is a light; b. the amplifier is an audio amplifier for providing a gate trigger signal which is derived from the input mechanical audio signal and the amplifier comprises a plurality of amplifier stages, one of the stages having a load impedance comprising the stator of a nonlinearly varying potentiometer and having the wiper of the potentiometer coupled to the input of the subsequent stage for variable adjustment and selection of an audio signal level which triggers the thyristor. 